The present invention relates to a sensor guide wire, and in particular to a sensor guide wire provided with a tip region.
Today, there is an increased need for invasive measurements of physiological variables. For example, when investigating cardiovascular diseases, it is strongly desired to obtain local measurements of blood pressure, flow and temperature in order to evaluate the condition of the subject under measurement. Therefore, methods and devices have been developed for disposing a miniature sensor inside the body of an individual at a location where the measurements should be performed, and for communicating with the miniature sensor in order to provide the physician or medical technician with critical information as to the status of a patient's condition. Typically, the miniature sensor is arranged at a distal end of a guide wire, which is generally known in the art, and used for example in connection with treatment of coronary disease.
The distal end of the guide wire is inserted into the body of a patient, for example into an opening into the femoral artery, and placed at a desired location. Once the guide wire is placed by the physician into the appropriate location, the miniature sensor can measure e.g. the blood pressure, temperature, position and/or flow. Measurement of blood pressure is a way to diagnose e.g. the significance of a stenosis. For evident reasons, the dimensions of the sensor and the guide wire are fairly small; the guide wire typically has a diameter of 0.35 mm. The sensor element may for example be embodied by an elongated, essentially rectangular chip with a pressure sensitive member in the form of a membrane provided thereon.
In order to power the sensor and to communicate signals representing the measured physiological variable to a control unit acting as an interface device disposed outside the body, one or more microcables for transmitting the signals are connected to the sensor, and are routed along the guide wire to be passed out from the vessel to an external control unit via a connector assembly. Most commonly extremely thin electrical cables are provided inside the guide wire, which itself is provided in the form of a tube (having an outer diameter of e.g. 0.35 mm), oftentimes made of stainless steel. In order to increase the bending strength and maneuverability of the tubular guide wire, a core wire is positioned inside the tube. The mentioned electrical leads are positioned in the space between the inner lumen wall and the core wire. Furthermore, the sensor chip is often arranged in a short tube, also referred to as a jacket or a sleeve. The jacket is hollow and accommodates, besides the sensor chip, also a portion of a core wire and often at least one microcable. A first coil may be attached to the distal end of the jacket, usually enclosing a distal tip portion of the core wire. Optionally a second coil may be attached to the proximal end of the jacket. The first and second coils may be attached to the respective end of the jacket, e.g. by gluing, welding or alternatively soldering. One purpose of the first coil is to enable steering the sensor guide wire through winding blood vessels. To help the user easily guide the wire through such tortuous vessel systems, the distal coil is often radiopaque, such that it is visible on an angiogram.
A large flexibility of the sensor guide wire is advantageous in that it allows the sensor guide to be introduced into small and tortuous vessels. It should, however, also be recognized that if the core wire is too flexible, it would be difficult to push the sensor guide forward into the vessels, i.e. the sensor guide wire must possess a certain “pushability” and a certain “torquability”. Additionally, the sensor guide must be able to withstand the mechanical stress exerted on the core wire especially in sharp vessel bends.
Several different designs of sensor guide wires are known in the prior art, and examples of such sensor guide wires are disclosed in U.S. Pat. No. 6,167,763 B1, which describes the cantilevered mounting of the sensor element, U.S. RE39863 E, which discloses the sensor element and U.S. Pat. No. 6,248,083 B1, showing the complete sensor guide wire assembly, which all are assigned to the same assignee as in the present application, and which are hereby all incorporated by reference for the medical devices, components, materials, techniques, and methods described therein.
A further example of a sensor guide wire is disclosed in WO 2009/054800 A1, assigned to the present assignee, which is incorporated by reference herein in its entirety for the medical devices, components, materials, techniques, and methods described therein. The sensor guide wire has a proximal shaft region, a flexible region and a distal sensor region, and a tip region. The tip region of the sensor guide wire is provided with a tip core wire at least partly enclosed by a distal coil.
To improve navigation through tortuous vessels or to ease crossing a lesion in the vessel, the user, typically a physician performing a procedure, will oftentimes manually shape the tip of the wire at a slight angle before inserting the sensor guide wire into the patient. During the progression of the insertion through the vessels, the physician will often remove the wire and reshape the tip several times by hand. The reshaping is done in two steps; 1) straightening of the wire tip back to its original shape and 2) reshaping of the wire to a desired curve. Repeating these steps increases the risk of inducing permanent deformation in the wire, leading to reduced mechanical performance and risk of breakage. Furthermore, it is time consuming for the user.